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WIP Wiki page: http://wiki.musicbrainz.org/User:HibiscusKazeneko/Sub-Publisher_Relationship

Right now, there is only a straight "publisher" relationship. This proposal would add a "sub-" attribute similar to the "co-" attribute used in certain artist ARs.
Ideally, this relationship would have a locale selection drop-down menu like [[Alias|Aliases]] have, since sub-publishers typically only have rights to entities (works, releases, etc.) in select countries or regions.